Compressor and method for controlling the compressor

Abstract

A compressor and a control method thereof are provided. The compressor includes a motor with a rotor of a permanent magnet. According to embodiments, the method of controlling the compressor includes: applying a detection current to the motor in response to a command of starting the compressor; detecting whether there is demagnetization of the permanent magnet of the rotor according to a response of the motor to the applied detection current; resetting an operating parameter of the compressor if there is the demagnetization; and starting the compressor according to the reset operating parameters. According to embodiments of the present disclosure, when the compressor is to be started, demagnetization is detected first, and the operating parameter are set accordingly, so as to suppress or avoid performance degeneration due to the demagnetization.

What is claimed: 
     
       1. A method of controlling a variable-speed compressor comprising a motor with a rotor of a permanent magnet, the method comprising:
 applying a detection current to the motor in response to a command of starting the compressor; 
 detecting, according to a response of the motor to the detection current, whether there is demagnetization of the permanent magnet of the rotor; 
 resetting an operating parameter of the compressor if there is the demagnetization; and 
 starting the compressor according to the reset operating parameter; 
 wherein the detection current has a q-axis component, with a d-axis component of zero, and the detection current is a predetermined percentage of a rated operating current of the compressor; 
 wherein detecting whether there is demagnetization of the permanent magnet of the rotor comprises: determining a level of demagnetization; and 
 wherein resetting an operating parameter of the compressor comprises: setting the operating parameter according to the level of demagnetization. 
 
     
     
       2. The method according to  claim 1 , wherein the detection current is around 60% of the rated operating current of the compressor. 
     
     
       3. The method according to  claim 2 , wherein detecting whether there is demagnetization of the permanent magnet of the rotor comprises:
 calculating a flux linkage of the permanent magnet; and 
 comparing the calculated flux linkage of the permanent magnet with a theoretical value of a flux linkage of the permanent magnet to determine whether there is the demagnetization or not. 
 
     
     
       4. A compressor, comprising:
 a compression mechanism, configured to compress working medium entering the compressor; 
 a motor with a rotor of a permanent magnet, configured to drive the compression mechanism to compress the working medium; and 
 a controller, configured to execute a startup algorithm at startup to operate according to the method of  claim 3 . 
 
     
     
       5. A compressor, comprising:
 a compression mechanism, configured to compress working medium entering the compressor; 
 a motor with a rotor of a permanent magnet, configured to drive the compression mechanism to compress the working medium; and 
 a controller, configured to execute a startup algorithm at startup to operate according to the method of  claim 2 . 
 
     
     
       6. The method according to  claim 1 , wherein a positional angle of the rotor obtained by integrating a speed of the motor is used in a control loop of the motor when detecting whether there is demagnetization of the permanent magnet of the motor. 
     
     
       7. The method according to  claim 1 , wherein the operating parameter reset comprise at least one of a maximum output current and an overcurrent protection point of a frequency converter which are operable for driving the motor in the compressor. 
     
     
       8. The method according to  claim 7 , wherein said resetting the operating parameter of the compressor if there is the demagnetization comprises:
 if there is the demagnetization and a level of the demagnetization is within 20%, increasing the maximum output current of the frequency converter and decreasing the overcurrent protection point with an increase in the level of the demagnetization. 
 
     
     
       9. The method according to  claim 8 , wherein the maximum output current of the frequency converter has an upper limit that is 150% of a rated operating current of the frequency converter, and the overcurrent protection point has a lower limit that is 160% of the rated operating current of the frequency converter. 
     
     
       10. A compressor, comprising:
 a compression mechanism, configured to compress working medium entering the compressor; 
 a motor with a rotor of a permanent magnet, configured to drive the compression mechanism to compress the working medium; and 
 a controller, configured to execute a startup algorithm at startup to operate according to the method of  claim 1 . 
 
     
     
       11. The compressor according to  claim 10 , further comprising an angle generator configured to obtain a positional angle of the rotor by integrating a speed of the motor. 
     
     
       12. The compressor according to  claim 10 , wherein the detection current has a q-axis component, with a d-axis component of zero. 
     
     
       13. The method according to  claim 10 , wherein the controller is further configured to detect whether there is demagnetization of the permanent magnet of the rotor by way of:
 calculating a flux linkage of the permanent magnet; and 
 comparing the calculated flux linkage of the permanent magnet with a theoretical value of a flux linkage of the permanent magnet to determine whether there is the demagnetization or not. 
 
     
     
       14. The method according to  claim 10 , wherein the controller is further configured to determine a level of demagnetization, and to set the operating parameter according to the level of demagnetization. 
     
     
       15. The method according to  claim 10 , wherein the operating parameter reset comprise at least one of a maximum output current and an overcurrent protection point of a frequency converter which are operable for driving the motor in the compressor. 
     
     
       16. The method according to  claim 15 , wherein the controller is configured to:
 increase the maximum output current of the frequency converter and decrease the overcurrent protection point with an increase in the level of the demagnetization if there is the demagnetization and a level of the demagnetization is within 20%. 
 
     
     
       17. The method according to  claim 16 , wherein the maximum output current of the frequency converter has an upper limit that is 150% of a rated operating current of the frequency converter, and the overcurrent protection point has a lower limit that is 160% of the rated operating current of the frequency converter. 
     
     
       18. The compressor according to  claim 10 , wherein the compressor is a variable-speed compressor and the variable speed compressor comprises a frequency converter.